<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>标题、段落</title>
</head>

<body>
    <h1>this is a heading</h1>
    <h2>this is a heading</h2>
    <h3>this is a heading</h3>
    <h4>this is a heading</h4>
    <h5>this is a heading</h5>
    <h6>this is a heading</h6>
    <!-- 水平线 -->
    <hr>
    <p>this is a paragraph</p>

</body>

</html>